Many types of spinal irregularities can cause pain, limit range of motion, or injure the nervous system within the spinal column. These irregularities can result from, without limitation, trauma, tumor, disc degeneration, and disease. Often, these irregularities are treated by immobilizing a portion of the spine. This treatment typically involves affixing a plurality of fixation devices to one or more vertebrae and connecting the devices to an elongate rod that generally extends in the direction of the axis of the spine. Typically, fixation devices may include a bone fastener (e.g., bone screw, hook, etc.) for coupling the fixation device to vertebra. Fixation devices further may include a head for coupling the bone fastener to the rod. The process of placing the rod within or adjacent to the head so that they can be coupled together is referred to as “reducing” the rod.
Rod reduction is commonly performed by a surgeon using his or her hands and/or rigid tools, such as pliers, levers, or other instrumentation adaptable to create the necessary pushing and/or pulling forces on the implanted fastener and rod. One current technique employs a reduction head attached to the head of the fixation device. The reduction head generally may include tabs that extend from each of the sidewalls of the head of the fixation device, wherein at least a portion of the inner surface of each of tabs is threaded. To reduce the rod into the head of the fixation device, a driving instrument can be threaded through the tabs. One drawback to this technique is that that the instrumentation typically must be higher as the rod needs to be seated at least below 1-2 threads in the channel between the tabs before the driving instrument can be engaged, resulting in larger equipment applying more weight to the implanted fastener. Another drawback to this technique is that, after the rod is reduced, the driving instrument must be unscrewed from the tabs before the tabs can be removed, increasing the time and complexity of the procedure.
Accordingly, there exists a need for new and improved apparatuses for rod reduction.